Sheet folding mechanism

ABSTRACT

A sheet folding mechanism particularly adapted for lengthwise folding so-called no-iron sheets. The device comprises a pair of work supporting arms, a first folding arm and a second folding arm. Automatic mechanism is operable to lower the work supporting arms to a position in which an operator can insert two corners of a sheet into clamping means on the outer ends of the work supporting arms. Upon such insertion, the arms are automatically elevated to a position to maintain the bottom of the sheet above the floor during the subsequent folding operations. The outer ends of the work supporting arms are swung in opposite directions to stretch the top of the sheet, whereupon the two folding arms are sequentially actuated to form two parallel folds lengthwise of the sheet. The successive operations of elevating the arms, stretching the sheet, and producing the two folds are performed by spring motors to avoid the creation of forces that could tear the sheets.

United States Patent [191 Gunn et al.

1451 May 20, 1975 SHEET FOLDING MECHANISM Inventors: David P. Gunn, Fort Lauderdale;

Fred May, Boca Raton, both of Fla.

[73] Assignee: Gunn-May Manufacturing, Inc.,

Fort Lauderdale, Fla.

Filed: Oct. 26, 1973 Appl. No.: 410,120

US. Cl. 270/61 R; 223/37 Int. Cl B65h 45/00 Field of Search 270/58, 61, 61 F, 62, 78,

Primary ExaminerRobert W. Michell Assistant Examiner-V. Millin Attorney, Agent, or Firm-Harry N. Schofer [5 7] ABSTRACT A sheet folding mechanism particularly adapted for lengthwise folding so-called no-iron sheets. The device comprises a pair of work supporting arms, a first folding arm and a second folding arm. Automatic mechanism is operable to lower the work supporting arms to a position in which an operator can insert two corners of a sheet into clamping means on the outer ends of the work supporting arms. Upon such insertion, the arms are automatically elevated to a position to maintain the bottom of the sheet above the floor during the subsequent folding operations. The outer ends of the work supporting arms are swung in opposite directions to stretch the top of the sheet, whereupon the two folding arms are sequentially actuated to form two parallel folds lengthwise of the sheet. The successive operations of elevating the arms, stretching the sheet, and producing the two folds are performed by spring motors to avoid the creation of forces that could tear the sheets.

19 Claims, 21 Drawing Figures 101 a B 1, 1 a

t 92 a .1 as 4o l as 42 4e 48 34 l ll 34 T' 24 2a 1 J so 1 4- 1 I6 16/ 14 ea 72 \N 1 l.--1oo n-l PATENTED MAY 2 01975 SHEET 1 OF 6 [FIGZA PATENT mmmms SHEET 3 OF 6 [Fl GTA [FIG] [FIGG PATE-NIEDHAY2U1975 SHEET WM 6 [FIG.I2

[FIGH- [FIGJIA PATENIEB HAY 2 01975 SHEET 5 OF 6 PATENTEB HAY 2 01975 Shirt? 6 UF 6 m 5: ms; 3E 23 m P r 1 Q2086 ofimlw wow Nam I W II 2! m9 0mm wwm Now MFG-us SHEET FOLDING MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the art of folding, and more particularly to a device adapted for folding so-called no-iron sheets, usually made from man made fibers such as polyesters or cotton-polyester blends,

Fabrics made from such fibers have the advantageous property of being relatively wrinkle free when washed and dried, and for this reason require little or no pressing. They are frequently described in the art as dripdry, in the sense that they can be suspended after being washed, and the water remaining in the fabric will run off by gravity, permitting quick drying.

The above property, as well as others, make sheets made from such fabrics particularly popular, especially for users of large quantities of sheets, such as hotels, motels and hospitals. The cost of laundering of cotton sheets involves an expensive item in the cost of operation, and many of such users have turned to sheets made from no-iron fabrics.

2. Description of the Prior Art Heretofore most of such users have had to resort to manual folding of the sheets when washed and dried, as the cost of folding machines on the market makes it economically impractical to purchase. The folding of sheets is a tedious, laborious and time consuming task, and it is becoming more and more difficult to recruit and keep competent employees. Moreover, as the field of such employees becomes smaller and smaller, their wages go up proportionately, adding to the cost of providing clean laundry.

SUMMARY OF THE INVENTION It is an object of this invention to provide a novel sheet folding mechanism which can be manufactured and sold in a price range that would be economically feasible for most users of large numbers of sheets.

It is a further object to provide a novel sheet folding mechanism that is simple and efficient in operation, and which does not require any particular skill to operate.

It is a still further object to provide a novel sheet folding mechanism that involves relatively few moving parts, and which takes up very little space.

It is a still further object to provide a novel sheet folding mechanism in which all folding operations are performed by spring motors, thus assuring that the sheets will not be overstressed and torn.

It is a still further object to provide a novel sheet folding mechanism that is fail safe in operation.

The attainment of the above and additional objects and advantages is accomplished by a novel mechanism and principle of operation in which a pair of pivoted work supporting arms having clamps on the outer ends are mounted and operated to bring the arms together in a lowered loading position in which the clamps are automatically opened to receive the corners on one end of a sheet to be folded. The clamps include switches, responsive to the presence of the corner of the sheet, to close the jaws, and when both clamps have been closed, a circuit is established to automatically initiate the folding cycle. The outer ends of both work supporting arms are simultaneously elevated, lifting the bottom of the sheet clear of the floor. The outer ends of the arms separate to hold the upper end of the sheet in a stretched position, whereupon a first folding arm swings across the mid portion of the upper end of the suspended stretched sheet to form a first fold therein while the work supporting arms are being brought together to maintain the upper end stretched during this operation. A second folding arm then moves transversely of the thus folded sheet to form a second fold therein parallel to the first fold, The operator grasps opposite sides of the folded sheet midway of its length, operates a release switch with the toe of the shoe of one foot, which opens the clamps and brings the work supporting arms and the first and second folding arms close together to release the tension in the sheet, per mitting the upper end to fall to form a fold transversey of the sheet. The operator can easily make a second transverse fold, thus completing the folding operation, which takes about five seconds.

All folding operations, including the operations of lifting and spreading the work. supporting arms, are performed by spring motors operating through levers, the springs being loaded by compressed air actuated servomotors which also move the arms in their non-folding directions. I

BRIEF DESCRIPTION OF THE DRAWINGS A clearer understanding of the inventionand its operation will become apparent from the following detailed description in conjunction with the annexed drawings, in which:

FIG. 1 is an elevation view of a preferred embodiment of the invention showing the parts in their inactive position;

FIGS. 2 and 2A are elevation and top plan views, re spectively, of the sheet folding device in its loading position, with the work supporting arms in their lowermost position to receive a work piece, FIG. 2A taken on the line 2A-2A of FIG. 2;

FIGS. 3 and 3A are elevation and top plan views, respectively, of the sheet folding device at the beginning of the folding cycle, showing the work supporting arms in their upward movement, FIG. 3A taken on the line 3A-3A of FIG. 3;

FIGS. 4 and 4A are elevation and top plan views, respectively, of the sheet folding device, showing the sheet in its stretched position and the first folding arm beginning to make the first fold in the sheet, FIG. 4A taken on the line 4A4A of FIG. 4;

FIGS. 5 and 5A are side and top plan views, respectively, of the sheet folding device, illustrating the position of the parts at the end of the first folding operation and with the second folding arm beginning to move to cause the second folding operation, FIG. 5A taken on the line 5A-5A of FIG. 5, and FIG. 5 taken on the line 5-5 of FIG. 5A;

FIGS. 6 and 6A are side and top plan views, respectively, of the sheet folding device, illustrating the positions of the various parts during the second folding operation, FIG. 6A taken on the line 6A-6A of FIG. 6, and FIG. 6 taken on the line 6-6 of FIG. 6A;

FIGS. 7 and 7A are elevation and top plan views, respectively, of the sheet folding device, illustrating the positions of the various parts at the termination of the second folding operation, with the hands of the operator grasping the mid point of the folded sheet to permit a transverse fold, FIG. 7A taken on the line 7A7A of FIG. 7;

FIGS. 8 and 8A are side and top plan views, respectively, of the sheet folding device, illustrating the relative positions of the parts at the end of the folding operation, with the hand of the operator holding the folded sheet and with his toe on the release switch, FIG. 8 taken on the line 8-8 of FIG. 8A;

FIG. 9 is a top plan view of the sheet folding device, illustrating in detail the various members and their relationship to each other;

FIG. 10 is an enlarged detail view of a portion of the structure of FIG. 9;

FIGS. 11 and 11A illustrate, in detail, the work supporting arms, showing the work gripping device in its closed and open position, respectively;

FIG. 12 is a side view taken on the line 12-12 of FIG. 10, illustrating the operating mechanism for elevating and lowering the work supporting arms; and

FIG. 13 is a diagrammatic representation of the electrical and fluid pressure circuits.

Referring to the annexed drawings in which the sheet folding mechanism is designated in its entirety by the numeral 10, the device includes a supporting structure comprising four corner legs 12 adapted to rest on the floor 13, the upper ends of the legs supporting a housing 14 for enclosing the various operating parts.

With particular reference to FIGS. 1, 9 and 10, there is shown a pair of hollow work supporting arms 16 supported for oscillation in a horizontal plane, one end of each arm being attached to the sprocket wheels 18 and 20, respectively, for movement in opposite directions. A chain 22 is reeved in opposite directions about the sprocket wheels, one end of the chain being attached to the sprocket wheel 18 and the other end to one end of a spring motor 24, the other end of the spring motor being secured to a fixed support 26.

The sprockets 18 and are mounted for rotation on a pair of spindles 28 carried by a rocker bar 30, the rocker bar being supported for oscillating or rocking motion on a shaft 32 supported at its ends in bearings 34. As shown in FIG. 12, a lever 36 is attached at one end to the shaft 32 and at its other end to a piston rod 38 of a servomotor 40. A spring motor 42 is secured at one end to the lever 36 and at its other end to a fixed support within the housing 14.

Referring to FIG. 10, a lever 44 is secured to the sprocket wheel 18, the outer end of the lever being pivotally attached to the outer end of a piston rod 46 of a servomotor 48, the servomotor being pivotally supported on the fixed support 26.

From the mechanism so far described, it is evident that the admission of fluid pressure to the bottom of the piston of the servomotor 40 in FIG. 12 will force the left hand end of the lever 36 upward to load the spring motor 42 and to lower the work supporting arms 16 from their elevated position to their lowered position, and that the release of fluid pressure from the servomotor will permit the loaded spring motor 42 to take over to oscillate the lever 36 in a counterclockwise direction to force the piston of the servomotor downward and to elevate the outer ends of the work supporting arms 16. Similarly, it is evident that the admission of fluid pressure to the right hand end of the servomotor 48 in FIG. 10 will be effective to oscillate the lever 44 and the sprocket wheel 18 counterclockwise and to oscillate the sprocket wheel 20 clockwise to load the spring motor 24, which operation will bring the outer ends of the work supporting arms 16 into juxtaposition as shown in FIG. 9, and that the release of fluid pressure from the servomotor 48 will permit the loaded spring motor 24 to take over to oscillate the sprocket wheel 20 and the work supporting arm 16 connected therewith in a counterclockwise direction, and to oscillate the sprocket wheel 18 and the work supporting arm 16 connected therewith in a clockwise direction to spread the outer ends of the arms 16 apart, and at the same time moving the lever 44 in a clockwise direction to force the fluid from the servomotor 48.

Referring to FIGS. 11 and 11A, the outer end of each of the work supporting arms 16 carries a work gripping device 50, in the form of a clamp including a movable member hinged at 52 adapted to be pressed against the head 54 by a compression spring motor 56. A cable 58 is attached to one end of the movable part of the clamp, passing through the coil spring 56 and through the hollow work supporting arm 16, the opposite end being secured to the movable core of a solenoid 60. Energization of the solenoid 60 will open the clamp as shown in FIG. 11A and also compress the spring motor 56, while deenergization of the solenoid 60 will permit the spring motor 56 to move the movable part of the clamp 50 to its clamping position shown in FIG. 11.

Each head 54 also carries a normally open clamp switch 62 adapted to be engaged by the insertion of a work piece to close the switch to initiate the folding cycle, as will be explained in detail later in this description, each switch being connected with a conductor 64 passing through the hollow arm 16 to actuate the solenoid 66 of a relay shown in FIG. 13.

A first folding arm 68 is shown in FIG. 9, the outer end having a bend therein and a depending finger 70 (see FIG. 1) adapted to engage the upper end ofa sheet to make a fold therein, as explained later in this specification. The folding arm 68 is pivoted at 72 intermediate the ends on the outer end of a supporting bar 74, the outer end of the folding arm being pivotally connected with a piston rod 76 of a servomotor 78. A rod 80 is pivotally connected at one end with the folding arm 68 to the left of the pivot 72, the other end of the rod being attached to one end of a spring motor 82, the other end of the spring motor being anchored at 84. The fixed end of the servomotor 78 is pivotally anchored at 86.

It is evident, from the foregoing description, that the admission of fluid under pressure to the lower end of the servomotor 78 in FIG. 9 will oscillate the folding arm 68 in a counterclockwise direction to a position past the position shown and will load the spring motor 82, and that the release of fluid pressure from the servomotor 78 will permit the spring motor 82 to take over to oscillate the folding arm in a clockwise direction, and at the same time will force the piston (not shown) of the servomotor in a downward direction to scavenge the air from the cylinder of the servomotor below the piston.

A second folding arm is shown in FIG. 9 at 88, being pivotally mounted at on the outer end of a supporting bar 92. An operating lever 94 is fixedly secured at approximately its midpoint to the folding arm 88 at its pivot point, the left hand end of the lever 94 being pivotally attached to the outer end of a piston rod 96 of a servomotor 98, the servomotor being pivotally anchored at 97. The right hand end of the lever 94 is attached to one end of a spring motor 99, the other end being anchored at 101. The outer or free end of the folding arm 88 includes a depending finger 100 (see FIG. 1) adapted to engage the upper end of a sheet to form a fold therein, as will be described more fully hereinafter.

From the foregoing description, it is evident that the admission of fluid under pressure to the lower end of the servomotor 98 in FIG. 9 will cause oscillation of the operating lever 94 and the folding arm 88 in a clockwise direction and will load the spring motor 99, and that the release of fluid pressure from the servomotor will permit the spring motor 99 to take over to oscillate the operating lever 94 and the folding arm 88 in a counterclockwise direction, moving the piston rod 96 downward to scavenge the pressure fluid from the cylinder of the servomotor below the piston therein (not shown).

FIG. 1 shows an off-on switch 102 secured to one of the supporting legs 12 in close proximity to an operator for starting the device.

Referring to FIG. 13, which diagrammatically illustrates the electrical and fluid pressure circuits, the numeral 104 designates a timer motor operating a shaft 106 on which are mounted, in spaced relation, a timer cam 108, a first fold cam 110, a second fold cam 112, and a work spread cam 114 adapted to control the work supporting arms 16. As will be described hereinafter, these cams control the timer motor and the sequential operations of the various members to form folds in a work piece, such as a sheet 326.

FIG. 13 also illustrates the fluid pressure circuit, which includes a supply conduit 116 receiving a supply of compressed air, and connected with a normally closed valve 136. A first branch 118 delivers air to a normally closed valve 120 under the control of a solenoid 122; a second branch 124 delivers air to a normally open valve 126 under the control of a solenoid 128, and a third branch 130 delivers air to a normally closed valve 132 under the control of a solenoid 134. The valve 136 is controlled by a solenoid 138.

All four valves 120, 126, 132 and 136 are of the same type. Valve 120 controls the flow of compressed air to and from the servomotor the valve 126 controls the flow of compressed air to and from the servomotor 48; the valve 132 controls the flow of compressed air to and from the servomotor 98; and the valve 136 controls the flow of compressed air to and from the servomotor 78. The four valves are of the type which, when in open position, permits the flow of compressed air to actuate the servomotor, and when in closed position, stops the flow of compressed air through the valve and connects the servomotor to the atmosphere.

OPERATION FIG. 13 diagrammatically illustrates the various movable parts in their inactive positions. In these positions, the work supporting arms 16 are in their elevated position under the force of spring motor 42, with the outer ends in close proximity to each other as shown in FIG. 1, due to the flow of compressed air to the servomotor 48 through the normally open valve 126. The first folding arm 68 occupies the position shown in FIG. 2A under the action of the spring motor 82, and the second folding arm 88 occupies the position shown in FIGS. 2A andd 9 under the action of the spring motor 99. The work gripping devices 50 are in their closed position under the influence of the spring motors 56, there being no flow of current to the actuating solenoids 60.

The safety switch 256 in the conductor 254 leading to the solenoid actuator 122 for the valve is in its closed position, being held in such position by a collar 324 on the piston rod 76 in FIG. 9, and the safety switch 258 in the conductor 254 leading to the solenoid actuator 122 is also closed and held in that position by contact with the lever 44 in FIG. 10.

The operator places a basket 328 of sheets 326 to be folded in position in front of the folding device 10, and closes the off-on switch 102, permitting a flow of current through the conductors 140, 144, movable switch member 148 of the release switch 146, fixed contact 150, conductors 152, 154, 162, 280, 174, movable switch member 170, contact 172, and conductor 176 to actuate one of the solenoids 60 to move one of the work gripping devices 50 to its open position, and through the conductors 282, 284, 286, movable switch member 210, contact 212 and conductor 214 to the other solenoid 60 to move the other work gripping device 50 to its open or work piece receiving position. Current also flows through the conductors 140, 320, 276, 278, 274, contact 272, movable switch member 268, conductors 266, 264, 254 and closed safety switches 256 and 258 to actuate the solenoid 122 to open the valve 120, allowing compressed air to flow from the conduit 116 and branch conduit 118 into the cylinder of the servomotor 40 to lower the work supporting arms to the position shown in FIGS. 2 and 2A, and at the same time loading the spring motor 42. Note, in FIG. 2A, that during this downward movement, the folding arms 68 and 88, which are pivoted for oscillating movement in a horizontal plane below the pivotal supports of the work supporting arms 16, have been moved to one side where they do not interfere with the movement of the work supporting arms 16 during their up and down movement.

The operator then inserts opposite end corners of a sheet 326 between the jaws of the open work gripping devices 50. As the corners of the sheet are inserted, they engage the open clamp switches 62 carried by the head 54, causing a flow of current through the conductors 140, 144, movable switch member 148, fixed contact 150, conductors 152, 154, 162, 164, closed clamp switch 62 and conductor 64 to energize the solenoid 66 of relay 2. Current also flows through the conductors 280, 282, 284, 226, closed clamp switch 62 and conductor 64 to energize the solenoid 66 of the relay 3. Energization of the relay 2 moves the movable switch members and 182 toward the left, bbreaking the flow of current to one of the work gripping devices 50, and energization of the relay 3 moves the movable switch members 210 and 188 toward the left, breaking the supply of current to the other work gripping device 50, permitting the spring motors 56 of the work gripping devices 50 to close the jaws to grip the corners of the sheet 326. At the same time, a flow of current passes through the conductor 174, movable switch member 170, contact 168 and conductors 166 and 164 to establish a holding circuit for the solenoid 66 of the relay 2, and a current passes through the conductors 284, 286, movable contact member 210, contact 208, and conductors 206 and 64 to establish a holding circuit for the solenoid 66 of the relay 3. Energization of both solenoids 66 of the relays 2 and 3 establishes a flow of current through the conductor 178, contact 180, movable switch member 182, conductor 186, movable switch member 188, contact 190, conductors 194, 216 and 218 to the'solenoid 220 of the relay 1, moving the movable switch members 158 and 268 toward the left, thereby breaking the circuit to the solenoid 122 and moving the valve 120 to its closed position, permitting the discharge of compressed air from the servomotor 40 to the atmosphere. The loaded spring motor 42 takes over, raising the work supporting arms 16, as shown in FIGS. 3 and 3A. The movable switch member 158 engages the contact 224, establishing a holding circuit through the conductors 156, 222 and 218 to the solenoid 220.

It should be noted, from the above description, that both clamp switches 62 must be closed before a circuit is established to the relay 1, thusassuring that the sequence of folding will not begin until both corners of the sheet 326 have been gripped by the work gripping devices 50.

When the work supporting arms 16 reach their elevated position, a collar 322 on the piston rod 38 of the servomotor 40 (FIG. 12) closes the arms-up switch 198 to establish a circuit through conductors 140, 144, movable switch member 148, contact 150, conductors 152, 154, 162, 280, 282, .178, contact 180, movable switch member 188, contact 190, conductors 194 and 196, arms-up switch 198, conductor 200, cam follower switch 202, and conductor 204 to energize the timer motor 102, causing clockwise rotation of the camshaft 106 and the cams 108, 110, 112 and 114 thereon. Cam follower 314 drops off the high point 316 of the cam 114 onto the dwell 318, allowing the cam follower switch 232 to meet with the contact 238, establishing a circuit through conductors 140, 320, 230, cam follower switch 232, contact 238, conductor 240 to energ'ize the solenoid 128, moving the valve 126 of the servomotor 48 to its closed position to allow the venting of the compressed air to the atmosphere. The loaded spring motor 24 (FIG. 9) now takes over, causing rotation of the sprocket wheel in a counterclockwise direction and the sprocket wheel 18 in a clockwise direction to move the work supporting arms 16 in opposite directions to stretch the upper end of the sheet 326 to the position shown in FIGS. 4 and 4A. At the same time the cam follower 304 drops from the high point 306 into the dwell 308 of the cam 112, permitting the cam follower switch 244 to engage the contact 246 to establish a circuit through the conductors 140, 320, 276, 242, cam follower switch 244, contact 246, and conductor 248 to energize the solenoid 134 to move valve 132 to its open position to permit flow of compressed air through the air conduit 116, branch 130, open valve 132 to the servomotor 98, causing the piston rod 96 (FIG. 9) to oscillate the operatinglever 94 and second folding arm 88 in a clockwise direction to the position shown in FIG. 4A, and load the spring motor 99.

Shortly thereafter, and before the spring motor 24 has moved the work supporting arms 16 to the sheet stretching position, the cam follower 294 rides off the high point 296 into the dwell 298 of the cam 110, permitting the cam follower switch 142 to engage the contact 299 to, establish a circuit through the conductors 140, 320, 276, 278, 279, cam follower switch 142, contact 299, and conductor 228 to energize the solenoid 138 to open valve 136, permitting compressed air to flow from the air conduit 116 through the open valve 136 into the servomotor 78 to move the piston rod 76 upward (FIG. 9) which oscillates the first folding arm 68 in a counterclockwise direction to a position past that shown in FIG. 9, loading the spring motor 82, and at the same time the collar 324 on the piston rod 76 opens the safety switch 256.

Continued rotation of the cam 110 causes the cam follower 294 to ride up onto the high point 300, breaking the circuit to the solenoid 138 and permitting the valve 136 to move to its closed position shown, so that the air may vent from the servomotor 78. The first folding arm 68, under the force of the loaded spring motor 82, moves in a clockwise direction from the position shown in FIGS. 4 and 4A to the position shown in FIGS. 5 and 5A to form the first fold in the sheet 326, the depending finger engaging the mid portion of the upper end of the suspended sheet as clearly seen in FlG.'4. While this is taking place, the cam follower 314 rides up onto the high point 316 of the cam 114 to break the circuit to the solenoid 128, permitting the valve 126 to reopen and allow compressed air from the conduit 116 and branch 124 to enter the interior of the servomotor 48 to bring the work supporting arms 16 together during the folding operation. Further rotation of the camshaft 106 causes the cam follower 304 to ride up onto the high point 310 of the cam 112, breaking the circuit to the solenoid 134, moving the valve 132 to itsclosed position and venting the air from the servomotor 98. A circuit is established through conductors and 154, which is parallel to the circuit through the release switch 146, for a purpose to be explained later in this description.

The loaded spring motor 99 becomes effective to oscillate the operating lever 94 and the second folding arm 88 in a counterclockwise direction during which the depending finger engages the upper end of the sheet 326, as shown in FIGS. 6 and 6A, to form the second fold therein. At the same time, the cam follower 294 drops into the dwell 302 of the cam 110, reestablishing the circuit to the servomotor 78 of the first folding arm 68, permitting the first folding arm to oscillate in a counterclockwise direction to follow the folding motion of the second folding arm 88, as seen in FIGS. 6, 6A, 7 and 7A. Further rotation of the camshaft 106 causes the cam follower 288 to drop into the dwell 292 of the cam 108, breaking the circuit through the conductor 200, cam follower switch 202 and conductor 204 to stop the timer motor 104 and establishing a circuit through contact 260, cam follower switch 202 and conductor 204 to the timer motor 104.

FIGS. 7 and 7A illustrate the positions of the work supporting arms 16, first folding arm 68 and second folding arm 88 at the termination of the first and second folding operations, the folded sheet 326 being supported by the work gripping devices 50, the depending finger 70 of the first folding arm 68 and the depending finger 100 of the second folding arm 88, the tension in the partly loaded spring motor 99 maintaining the upper end of the sheet 326 stretched to prevent it from dropping. The operator then grasps, with his hands 330, the opposite sides at the mid portion of the suspended sheet, as shown in FIG. 7, and with the toe 332 of his shoe, operates the release switch 146 conveniently disposed on the floor 13 withinreach of the operator. Operation of the release switch 146 moves the movable switch member 148 to the left as seen in FIG. 13, establishing a circuit through the contact 250, conductors 252, 264 and 262, contact 260, cam follower switch 202 and conductor 204 to reenergize the timer motor 104, producing further rotation of the cam shaft 106, permitting the cam follower 304 of the cam 112 to momentarily drop into the dwell 312 thereby reestablishing the circuit to the solenoid 134 to open the valve 132 to pressurize the servomotor 98, moving the second folding arm 88 clockwise in FIG. 8A to release the tension on the folded sheet 326. The parallel circuit established by cam follower 304, described above, momentarily continues the holding circuit to the relays l, 2 and 3. However, as soon as the cam follower 304 drops into the dwell 312, all circuits to the solenoids of the relays 1, 2 and 3'are broken, and the parts thereof return to the positions shown in FIG. 13. This reestablishes the circuit to energize the solenoids 60 to open the gripping devices 50, allowing the upper portion of the sheet 326 to drop and form a transverse fold in the sheet as seen in FIG 8. The operator can then easily form a second transverse fold in the sheet and deposit the thus folded sheet on one of the shelves 334. In view of the fact that the collar 324 on piston rod 76 is in a position spaced from the normally open switch 256 (FlG. 9), the actuation of the release switch 146 at this point will not energize the solenoid 122.

The cam follower 304, having momentarily dropped into the dwell 312 as described above, quickly rides up the high point 306 to break the circuit to the solenoid 134,- allowing the valve 132 to connect the servomotor 98 with the atmosphere, whereupon the spring motor 99 moves the second folding arm 88 to the position shown in FIG. 9.

The cam follower 294 shortly thereafter rides up onto the high point 296 of the cam 110, breaking the circuit to the solenoid 138, movingthevalve 136 to the position shown in FIG. 13 and venting the compressed air from the servomotor 78 to the atmosphere, the spring motor 82 rotating the first folding arm 68 in a clockwise direction under the force of the spring motor 82, as indicated by the arrow in FIG. 9, to close the safety switch 256.

Continued rotation of the timer motor 104 causes the cam follower 288 to ride up onto the high point 290 of the cam 108, breaking the circuit through conductor 262, contact 260, cam follower switch 202 and conductor 204, deenergizing the timer motor 104 and bringing the device to a halt, thus completing one folding cycle.

If the on-off switch 102 remains in its on position, a circuit is completed through conductors 140, 320, 276, 278, 274, contact 272, movable switch member 268, conductors 266, 264, 254, safety switches 256 and 258 to energize solenoid 122 to open the valve 120, permitting compressed air to enter the servomotor 40 to lower the work supporting arms 16 and to load spring motor 42. The solenoids 60 open the work gripping devices 50, and the device is in position to be loaded with a sheet 326 to begin another folding cycle.

Instead of having the solenoids 60 directly operating the work gripping devices 50, it is evident that they could operate through a fluid pressure actuated servomotor.

It is evident that the device 10 can operate to fold single, double, queen size and king size-sheets without any modification.

From the foregoing, it is seen that all movements of the device involved in the actual folding operations, such as gripping the sheet, elevating and separating the work supporting arms to maintain the top of the sheet stretched, the folding movements of the first and second folding arms, are under the control of spring motors, assuring that no undue stresses will be exerted on the sheet undergoing folding.

Although the preferred embodiment describes the folding of a sheet, it is evident that the scope of the invention is readily applicable to the folding of other objects, for example, pillow slips and large towels.

We claim:

1. A sheet folding mechanism, comprising: a supporting structure; a pair of separated work supporting arms; gripping means attached to one end of each of said arms for gripping a work piece; spaced first-pivotal means attached to the other end of each of said arms for permitting movement of said arms in a predetermined plane; second pivotal means mounting said first pivotal means for permitting movement of said arms in a second planar direction normal to said first plane; means operating said arms for movement from a first position in which said one ends are lowered and in close proximityto each otherfo r attachment to said gripping means of an elongated work piece to be folded, and for. movement to another position in which the said one ends are disposed in spaced, elevated, relation to retain the attached end of the work piece in stretched condition and the lower end of the work piece spaced from the floor; folding means; means mounting said folding means for movement into engagement with the stretched work piece forming one or more folds therein while the outer ends of the work supporting arms are brought into proximity with each other in an elevated position; and means operable to release said work gripping means.

2. A sheet folding mechanism as defined in claim 1, includingmeans moving said work supporting arms travel through an intermediate path in which the said one ends are being elevated while remaining in close proximity.

3. A sheet folding mechanism as defined in claim 1, in which said folding means comprise at least one folding arm.

4. A sheet folding mechanism as defined in claim 1, in which each of said work gripping means includes means responsive to the presence ofa work piece to automatically move said work gripping means to a gripping position.

5. A sheet folding mechanism as defined in claim 4, in which said means responsive to the presence of a work piece includes a spring motor.

6. A sheet folding mechanism as defined in claim 5, including electromagnetic means connected with said work gripping means operable, when energized, to open the gripping means and to load said spring motor, and to permit closing of the gripping means when deenergized.

7. A sheet folding mechanism as defined in claim 4, in which said means responsive to the presence of a work piece includes means to initiate a work folding cycle.

8. A sheet folding mechanism as defined in claim 7, in which the means responsive to the presence of a work piece includes a pair of switches, one of said switches carried by each of said gripping means in a position to be actuated by the presence of a work piece, and a folding initiating circuit, said switches being disposed in series in said circuit whereby said folding cycle is initiated when a work piece engages both of said switches. I

9. A sheet folding mechanism as defined in claim 1, including first and second folding arms, and means mounting said folding arms for movement in sequence from a first position clear of the work piece to a work piece engaging position to form folds therein.

10. A sheet folding mechanism as defined in claim 9, in which said folding arms are mounted for swinging movement in a horizontal plane, each arm having a depending portion engaging the upper end of the work piece when suspended, in stretched condition, by said work supporting arms.

11. A sheet folding mechanism as defined in claim 10, including automatic means operable through a cycle to move the work supporting arms from an initial position, in which the outer ends thereof are elevated, to said first position, through said intermediate position and to said other position, to move said first folding arm from a position remote from the work piece to a work piece engaging position, the outer ends of said work supporting arms being simultaneously moved toward each other whereby the continued movement of the first folding arm, in cooperation with the work supporting arms, retains the work piece in stretched condition during the first folding operation, moving said second folding arm from a position remote from the work piece to a folding position in engagement with the work piece, reversing the direction of movement of said first folding means during said second folding operation to retain the work piece in stretched condition, and returning the first and second folding arms to their respective positions remote from the work piece after the work piece has been removed.

12. A sheet folding mechanism as defined in claim 11, including means to initiate actuation of said automatic means, and means to stop said automatic means at the termination of a cycle.

13. A sheet folding mechanism as defined in claim 12, including manually controlled means to release said work gripping means.

14. A sheet folding mechanism as defined in claim 11, in which said automatic means includes fluid pressure means to actuate said work supporting arms and said first and said second folding arms, and timer controlled means to regulate the flow of fluid under pressure to said fluid pressure actuated means.

15. A sheet folding mechanism as defined in claim 14, in which said timer controlled means includes cams and electric circuits to actuate said fluid pressure means in a predetermined sequence.

16. A sheet folding mechanism as defined in claim 14, including fluid pressure means to actuate said work supporting arms from an elevated position to a lowered position.

17. A sheet folding mechanism as defined in claim 15, in which said fluid pressure means includes servomotors to actuate said work supporting arms, said first folding arm and said second folding arm in one direction, and spring motors to actuate said arms in an opposite direction.

18. A sheet folding mechanism as defined in claim 17, in which the spring motors are loaded by the fluid pressure actuation of said servomotors.

19. A sheet folding mechanism as defined in claim 18, in which said work supporting arms, first folding arm and second folding arm are actuated by said spring motors during the work piece folding operations. 

1. A sheet folding mechanism, comprising: a supporting structure; a pair of separated work supporting arms; gripping means attached to one end of each of said arms for gripping a work piece; spaced first pivotal means attached to the other end of each of said arms for permitting movement of said arms in a predetermined plane; second pivotal means mounting said first pivotal means for permitting movement of said arms in a second planar direction normal to said first plane; means operating said arms for movement from a first position in which said one ends are lowered and in close proximity to each other for attachment to said gripping means of an elongated work piece to be folded, and for movement to another position in which the said one ends are disposed in spaced, elevated, relation to retain the attached end of the work piece in stretched condition and the lower end of the work piece spaced from the floor; folding means; means mounting said folding means for movement into engagement with the stretched work piece forming one or more folds therein while the outer ends of the work supporting arms are brought into proximity with each other in an elevated position; and means operable to release said work gripping means.
 2. A sheet folding mechanism as defined in claim 1, including means moving said work supporting arms travel through an intermediate path in which the said one ends are being elevated while remaining in close proximity.
 3. A sheet folding mechanism as defined in claim 1, in which said folding means comprise at least one folding arm.
 4. A sheet folding mechanism as defined in claim 1, in which each of said work gripping means includes means responsive to the presence of a work piece to automatically move said work gripping means to a gripping position.
 5. A sheet folding mechanism as defined in claim 4, in which said means responsive to the presence of a work piece includes a spring motor.
 6. A sheet folding mechanism as defined in claim 5, including electromagnetic means connected with said work gripping means operable, when energized, to open the gripping means and to load said spring motor, and to permit closing of the gripping means when deenergized.
 7. A sheet folding mechanism as defined in claim 4, in which said means responsive to the presence of a work piece includes means to initiate a work folding cycle.
 8. A sheet folding mechanism as defined in claim 7, in which the means responsive to the presence of a work piece includes a pair of switches, one of said switches carried by each of said gripping means in a position to be actuated by the presence of a work piece, and a folding initiating circuit, said switches being disposed in series in said circuit whereby said folding cycle is initiated when a work piece engages both of said switches.
 9. A sheet folding mechanism as defined in claim 1, including first and second folding arms, and means mounting said folding arms for movement in sequence from a first position clear of the work piece to a work piece engaging position to form folds therein.
 10. A sheet folding mechanism as defined in claim 9, in which said folding arms are mounted for swinging movement in a horizontal plane, each arm having a depending portion engaging the upper end of the work piece when suspended, in stretched condition, by said work supporting arms.
 11. A sheet folding mechanism as defined in claim 10, including automatic means operable through a cycle to move the work supporting arms from an initial position, in which the outer ends thereof are elevated, to said first position, through said intermediate position and to said other position, to move said first folding arm from a position remote from the work piece to a work piece engaging position, the outer ends of said work supporting arms being simultaneously moved toward each other whereby the continued movement of the first folding arm, in cooperation with the work supporting arms, retains the work piece in stretched condition during the first folding operation, moving said second folding arm from a position remote from the work piece to a folding position in engagement with the work piece, reversing the direction of movement of said first folding means during said second folding operation to retain the work piece in stretched condition, and returning the first and second folding arms to their respective positions remote from the work piece after the work piece has been removed.
 12. A sheet folding mechanism as defined in claim 11, including means to initiate actuation of said automatic means, and means to stop said automatic means at the termination of a cycle.
 13. A sheet folding mechanism as defined in claim 12, including manually controlled means to release said work gripping means.
 14. A sheet folding mechanism as defined in claim 11, in which said automatic means includes fluid pressure means to actuate said work supporting arms and said first and said second folding arms, and timer controlled means to regulate the flow of fluid under pressure to said fluid pressure actuated means.
 15. A sheet folding mechanism as defined in claim 14, in which said timer controlled means includes cams and electric circuits to actuate said fluid pressure means in a predetermined sequence.
 16. A sheet folding mechanism as defined in claim 14, including fluid pressure means to actuate said work supporting arms from an elevated position to a lowered position.
 17. A sheet folding mechanism as defined in claim 15, in which said fluid pressure means includes servomotors to actuate said work supporting arms, said first folding arm and said second folding arm in one direction, and spring motors to actuate said arms in an opposite direction.
 18. A sheet folding mechanism as defined in claim 17, in which the spring motors are loaded by the fluid pressure actuation of said servomotors.
 19. A sheet folding mechanism as defined in claim 18, in which said work supporting arms, first folding arm and second folding arm are actuated by said spring motors during the work piece folding operations. 